Vehicle door latch devices include those, each having an interlocking unit assembly and an operating unit assembly integrated with each other, the interlocking unit assembly including: a body, which is fixed to a door and made of synthetic resin; and an interlocking mechanism, such as a latch and a pawl, the latch being accommodated in the body and engageable with a striker on a vehicle body side, and the pawl being engageable with the latch, and the operating unit assembly including: a casing fixed to a reverse side of the body; and an operating mechanism, which is assembled in the casing and is able to switch over the door between a locked state and an unlocked state by operations on the interlocking mechanism (see Patent Literatures 1 and 2).